<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="UTF-8">
        <title>margin</title>
        <style>
            .a{
                height: 100px;
                width: 100px;
                background-color: greenyellow;
                border: 5px solid yellow;
                margin: 50px
            }
            .b{
                height: 209px;
                width: 209px;
                background: #ffaaea;
                border: 1px dashed white;
                margin: 1px
            }
            .c{
                height: 213px;
                width: 213px;
                background: #ffaaea;
                border: 1px dotted white;
                margin: 40px
            }
            .d{
                height: 295px;
                width: 295px;
                background: #ffaaea;
                border: 1px solid white;
                margin: 20px
            }
            .e{
                height: 340px;
                width: 340px;
                background: white;
                border: 5px solid #a7fff8;
                margin: 27px
            }
            .f{
                height: 400px;
                width: 400px;
                background: white;
                border: 1px dashed black ;
                margin: 20px auto 0;
            }
        </style>
    </head>
    <body>
    <div class="f">
        <div class="e">
            <div class="d">
                <div class="c">
                    <div class="b">
                        <div class="a"></div>
                    </div>
                </div>
            </div>
        </div>
    </div>
    </body>
</html>